Overview.
What it is. Quercetin is a flavonoid — a class of antioxidant plant compounds — found in apples, onions, leafy greens, and berries. As a supplement it is extracted from plants like the Japanese sophora tree or produced by bacterial fermentation. It is a yellow crystalline powder that dissolves poorly in water but better in fats and alcohols.
How it works. Quercetin works mainly by stabilizing mast cells, the immune cells that release histamine in allergic reactions. When mast cells are more stable, they release less histamine in response to allergens like pollen or dust mites. It also has antioxidant and mild anti-inflammatory effects through inhibition of inflammatory enzymes. The mast cell stabilization is what gives quercetin its reputation for helping with itching and seasonal allergies.
Typical dose for dogs.
Small dogs (under 25 lbs): 50-100 mg twice daily
Medium dogs (25–50 lbs): 150-300 mg twice daily
Large dogs (50+ lbs): 300-500 mg twice daily
Safety: Quercetin is generally safe at supplement doses for dogs. The main concern is high-dose, long-term use, which has shown kidney effects in lab animals — stay within recommended doses. Avoid in dogs on kidney medications without vet guidance. Mild GI upset is the most common side effect.
Why itching is so frustrating to treat
Allergic itching in dogs has many possible triggers — pollen, dust mites, grass, food, flea saliva, contact allergens. Standard treatments include antihistamines (often poorly effective in dogs), corticosteroids (effective but with significant side effects on long-term use), and newer prescription drugs like Apoquel and Cytopoint. Quercetin is a gentler over-the-counter option for dogs with mild seasonal itching that does not warrant prescription medication. It will not match Apoquel for severe atopic dermatitis but can take the edge off mild allergy weeks.
Pairing with bromelain for absorption
Pure quercetin is poorly absorbed in the dog gut. Most commercial allergy formulas combine it with bromelain, an enzyme from pineapple that improves quercetin absorption and adds mild anti-inflammatory effects of its own. The combination is the standard form for clinical use. Quercetin without bromelain or a lipid carrier is much less likely to produce noticeable effects.
Realistic expectations
For mild seasonal itching, quercetin can reduce symptom intensity over 2-4 weeks of consistent use. It works best when started before allergy season peaks rather than during an active flare. For severe or year-round atopic dermatitis, quercetin alone is unlikely to be enough — it sits alongside, not instead of, prescription treatment in those cases.
In our line.
Not currently in any PawBite product — but we get a lot of questions about it.